Organic Synthesis Flashcards
Identify a reagent which could be used to distinguish between an aldehyde and a ketone. State what is observed when this reagent is added to each of these compounds in turn.
Tollens’ reagent - [Ag(NH₃)₂]⁺ - Silver mirror with the aldehyde.
Fehling’s solution - Cu²⁺ - Red ppt. with the aldehyde.
Identify a reagent which could be used to distinguish between an ester and a carboxylic acid. What would be observed when this reagent is added to each of them in turn.
NaHCO₃
No reaction is observed with the ester.
Effervescence is observed with the carboxylic acid.
What is observed when acidified potassium dichromate is added to an aldehyde?
A colour change from orange to green.
What is observed when acidified potassium dichromate(VI) is added to a ketone?
Nothing - ketones cannot be oxidized easily as strong C-C bonds must be broken.
How can a nitrile be formed from a haloalkane? What type of mechanism does this reaction have?
By reacting the haloalkane with KCN in aqueous and ethanolic solution to form a hydrogen halide and the nitrile.
This reaction has a nucleophillic substitution mechanism.
How can an amine be formed from a nitrile? Why does this method give a purer product than reducing a haloalkane with ammonia?
By reducing it using hydrogen and a nickel catalyst under heat and pressure. This is called catalytic hydrogenation. Because only the primary amine can be formed (no secondary, tertiary or quaternary salts nonsense here).
What can methyl esters be used as?
Biodiesel.
State and explain the difference in base strength between phenylamine and ammonia.
Phenylamine is a weaker base than ammonia.
In phenylamine the nitrogen’s lone pair is relocalize with the benzene ring’s electrons.
Delocalisation makes molecules more stable and less likely to donate electrons.
This delocalisation results in a weaker negative dipole on the nitrogen.
How can a mixture of amino acids formed by hydrolysis of a protein be seperated?
Electrophoresis.
Name a method of forming a amine that doesn’t involve a nitrile.
What are the conditions for this reaction?
Reduction of a haloalkane with ammonia.
An excess of ammonia and heat are required.
What is Friedel-Crafts acylation?
It is the addition of an acyl group to benzene.
This reaction requires an AlCl₃ catalyst, a non-aqueous environment and heat under reflux.
The acyl chloride is the electrophile in the electrophillic substitution mechanism.
What is the nitration of benzene? What are the conditions it requires?
It is the addition of a nitrate (NO₂) group to a benzene ring.
This reaction requires a conc. HNO₃ reagent, a conc. sulphuric acid catalyst and warmth.
The nitromium ion (NO₂⁺) is the electrophile in this reaction.
What is the by-product the nitration of benzene?
Water.
How can phenylamine be formed from nitrobenzene? What is the equation for this reaction?
By reducing the nitrobenzene with hydrogen and a tin+hydrochloric acid catalyst at room temperature.
Nitrobenzene + 6[H] —> phenylamine + 2H₂O
When phenylamine is being manufactured, it is reacted with hydrogen using a HCl catalyst. This forms a salt which needs dissociating in order for the phenylamine to be freed. What is this salt and what must be added to dissociate it?
C₆H₅NH₃⁺Cl⁻ + NaOH —-> C₆H₅NH₂ + H₂O + NaCl
